How do you determine the mass of potassium in 33.5 g of KCl?

To determine the mass of potassium (K) in 33.5 g of potassium chloride (KCl), you can follow these steps:

### Step 1: Determine the Molar Mass of KCl

First, you need to find the molar masses of potassium (K) and chlorine (Cl) and then calculate the molar mass of KCl.

- Molar mass of Potassium (K): approximately 39.10 g/mol
- Molar mass of Chlorine (Cl): approximately 35.45 g/mol

Now, calculate the molar mass of KCl:

\[
\text{Molar mass of KCl} = \text{Molar mass of K} + \text{Molar mass of Cl} = 39.10 \, \text{g/mol} + 35.45 \, \text{g/mol} = 74.55 \, \text{g/mol}
\]

### Step 2: Calculate the Moles of KCl

Next, use the mass of KCl to find the number of moles:

\[
\text{Moles of KCl} = \frac{\text{mass of KCl}}{\text{molar mass of KCl}} = \frac{33.5 \, \text{g}}{74.55 \, \text{g/mol}} \approx 0.449 \, \text{mol}
\]

### Step 3: Determine the Moles of Potassium in KCl

In KCl, there is one mole of potassium (K) for every mole of KCl. Thus, the number of moles of potassium is the same as the number of moles of KCl:

\[
\text{Moles of K} = \text{Moles of KCl} \approx 0.449 \, \text{mol}
\]

### Step 4: Calculate the Mass of Potassium

Finally, use the number of moles of potassium to find its mass:

\[
\text{Mass of K} = \text{moles of K} \times \text{molar mass of K} = 0.449 \, \text{mol} \times 39.10 \, \text{g/mol} \approx 17.55 \, \text{g}
\]

### Conclusion

The mass of potassium in 33.5 g of KCl is approximately **17.55 grams**.